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I have been asked to explain DRM. DRM is a digital radio transmission
format that can be heard on shortwave in the US and on medium wave in certain other places
in the world. When decoded (and this is what I am working on now), the audio is better
than regular shortwave audio.
Some say it is near FM quality. It moves towards FM quality anyway. It is pretty much in
the experimental phase right now. Once you take a listen on a regular receiver, you will know what it sounds like.
This is not the same as the current US AM radio digital transmissions they are
experimenting with now. If you are the type of person that likes to experiment,
then DRM might keep you happy. This section of my site is very new and will likely
get it's own area. It depends on if I have anything worthwhile to say about the
subject. So I am learning now. Below are some of my progress notes. They aren't
dated, but you get the idea.
Well folks, this is my third try at receiving DRM signals.
So far, no success. I am beginning to wonder if the problem is my soundblaster
sound card? I have tried 6140 and 9800 khz.
My first attempt was to use my Regen-O-Flex
receiver that I recently built. I saw on
Jogi's German Tube Site
site that someone was receiving DRM with a regenerative radio. All I could get was
the station ID. Then I tried my NC-125 by tapping off at the detector and moving the
BFO 12 khz off center. Still only a station ID.
My third attempt is with a tube direct conversion receiver. I haywired a little
6BE6 tube as a mixer with a 12 khz output. Still no reception.
One person suggests that my oscillator is not stable enough and that
this might be the problem. A crystal controlled oscillator might be what is needed.
This is next on my list.
Guess what? It works! It is off more than it is on but it is decoding!
With crystal control and maybe a little audio filtering, it should work better.
As I learn more, I will post more here. Not bad for one tube (and a Pentium III
computer).
Below are screen shots during reception of Radio China broadcast on 6140 khz
as relayed by the CBC. This system is not ready for primetime yet and perhaps
it never will. If I can get this together well enough, I will put up a separate
DRM section on my website.
My future thoughts are:
To add an rf amplifier with a little agc
To build a bandpass filter for the DRM output.
Have optional crystal control and vfo tuning.
Multiband tuning
Build this all on a chassis and make a stable vfo.
Add an audio stage for monitoring and a stand alone direct conversion radio (cw and ssb reception).
Should I use solid state instead of tubes?
Your comments are welcome. Bitte schreib' mich an.
Good dx de N2DS!
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